Growth is listed as "from $100/month billed annually", what does that actually work out to?

I am building a budget line for this and the "from $100/month billed annually" wording is throwing me off. Is $100 a monthly charge I get billed each month, or is it a yearly commitment quoted as a monthly figure?

And what does the annual option actually save versus paying month to month. I want the number spelled out before I put it in the sheet not a vague "you save by committing".